As well-described in U.S. Pat. No. 6,666,160, to Örneblad, “since man first ventured onto water in boats, he has tried to design hulls that increase speed without unduly sacrificing stability.” One avenue for reducing the hydrodynamic drag on a hull, and therefore improve hull efficiency in high-performance watercraft, is to provide a stepped hull wherein the lower surface of the hull is not a smooth surface, but rather includes transverse steps. Stepped hulls can be used to improve the performance of a hull by improving the on-plane performance characteristics, thereby reducing the wetted surface of the hull. Stepped hulls have been known for years, including, for example, U.S. Pat. No. 1,121,006, to Fauber, U.S. Pat. No. 1,858,030, to Batty, and U.S. Pat. No. 6,250,246, to Hubley, each of which is hereby incorporated by reference.
Fauber discloses a hull having a plurality of stepped portions, or “hydroplane members,” and an internal air duct system for delivering air under pressure to the stepped portions of the hull, for example, using the drive IC engine as a pump to force air into the internal air duct system. Hubley discloses an internal air duct system having entry openings near the bow of the hull and exit openings in the face of a step on the hull. These forced air systems assist in avoiding producing a vacuum in the stepped hull portions, and in lifting the hull out of the water, reducing the wetted area.
However the internal duct systems are relatively complicated to incorporate into a hull. Also, a common problem with stepped hulls are that during turns the boat may tend to spin generally about the step on the hull, particularly when a forced air system is tending to lift the aftward portion of the hull away from the water.